Design and fabrication of a novel superhydrophobic surface based on a copolymer of styrene and bisphenol A diglycidyl ether monoacrylate

Article abstract of DOI:10.1039/c4ra01505c

The copolymer of styrene and bisphenol A diglycidyl ether monoacrylate (PS-co-AADGEBA) was synthesized by three steps from raw materials, and then it was used to fabricate a superhydrophobic surface via a phase separation method. In particular the superhydrophobic surface not only exhibits superhydrophobicity towards water and corrosive liquids, including acidic and basic solutions, but also shows good transparency, improved robustness and excellent aging resistance. Furthermore, the PS-co-AADGEBA was also successfully grafted onto the surface of amino-functionalized hollow silica nanospheres (HSNs-NH ₂), then a (PS-co-AADGEBA)-g-(HSNs-NH₂) nanocomposite superhydrophobic surface was prepared. The obtained surfaces are promising materials for numerous potential application fields, including electronics, biomedical, martial and defense-related areas.

Full text of DOI:10.1039/c4ra01505c

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Design and fabrication of a novel
superhydrophobic surface based on a copolymer of
styrene and bisphenol A diglycidyl ether
monoacrylate†
Cite this: RSC Adv., 2014, 4, 18025
a
a
a
a
Jin-Qiu Liu, Chong Bai, De-Dong Jia, Wei-Liang Liu, Fu-Yan He,a Qin-Ze Liu,a
*
Jin-Shui Yao,a Xin-Qiang Wangb and Yong-Zhong Wub
The copolymer of styrene and bisphenol A diglycidyl ether monoacrylate (PS-co-AADGEBA) was
synthesized by three steps from raw materials, and then it was used to fabricate a superhydrophobic
surface via a phase separation method. In particular the superhydrophobic surface not only exhibits
superhydrophobicity towards water and corrosive liquids, including acidic and basic solutions, but also
shows good transparency, improved robustness and excellent aging resistance. Furthermore, the PS-co-
AADGEBA was also successfully grafted onto the surface of amino-functionalized hollow silica
nanospheres (HSNs-NH2), then a (PS-co-AADGEBA)-g-(HSNs-NH2) nanocomposite superhydrophobic
surface was prepared. The obtained surfaces are promising materials for numerous potential application
fields, including electronics, biomedical, martial and defense-related areas.
Received 20th February 2014
Accepted 1st April 2014
DOI: 10.1039/c4ra01505c
www.rsc.org/advances
suitable for practical applications due to limited mechanical
robustness of surface structures.
1. Introduction
Surfaces with water contact angles (WCA) greater than 150ꢀ and
sliding angles (SA) less than 10ꢀ are classied as super-
hydrophobic surfaces, which have attracted considerable
interest over the past few decades. Generally, two strategies are
adopted for the fabrication of superhydrophobic surfaces. One
is to roughen a low surface energy material, and the other is to
make a rough substrate and modify it with low surface energy
materials.1 Various techniques, template/hydrothermal
method, self-assembly, chemical vapor deposition, electro-
chemical etching, and electrodeposition, have been used to
fabricate superhydrophobic surfaces.2–12 Meanwhile, different
applications of which have been developed, for example, drag-
reducing/anti-icing/anti-reective surfaces, tunable wetting,
microuidic transportation, electroactive anticorrosive coatings
and oil/water separation as well as reduction of bacterial
adhesion.13–20 However, the superhydrophobic surfaces gener-
ated via current surface modication techniques are mostly not
Styrene (St) is the common low surface energy material in
superhydrophobic area and easily acquired for practical
application. Polymeric materials have been developed for the
preparation of superhydrophobic surfaces, for instance the
superhydrophobic surfaces prepared from a segmented
polydimethylsiloxane-urea copolymer,
a polyether based
polyurethaneurea, poly(methyl methacrylate), polystyrene
(PS), polycarbonate and a crosslinked epoxy resin are all
discussed.21 Superhydrophobic surfaces obtained by adding
ethanol to the PS solution of tetrahydrofuran was ever
reported by Zhiqing Yuan et al.22 Shuaixia Tan et al. created
Brassica oleracea-like polymer surface using amorphous PS
and demonstrated that the unitary micro-scale structure for a
polymer surface can exhibit outstanding water repellency as
natural lotus.23 In particular, PS based superhydrophobic
lms prepared by non-solvent induced phase separation
method using tetrahydrofuran (THF) as the solvent and
different alcohols as non-solvents were discussed.24 A major
problem of PS surfaces is that the poor resistance to
mechanical abrasion. The adhesion of PS lm to most
substrates, especially polar substrates, is generally poor. A
cast lm of PS onto glass or silicon is easy to peel off, it could
result in complete loss of the superhydrophobicity when
immersed in water.25
aSchool of Materials Science and Engineering, Qilu University of Technology, Key
Laboratory of Amorphous and Polycrystalline Materials, Key Laboratory of
Processing and Testing Technology of Glass Functional Ceramics of Shandong
Province, Daxue Road, Western University Science Park, Jinan 250353, PR China.
E-mail: wlliu@sdu.edu.cn; liuwl@qlu.edu.cn; Fax: +86-531-89631226; Tel: +86-531-
89631227
bState Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, PR
Similarly, epoxy resin is one of the most important thermo-
setting polymers widely used as structural adhesives, coating,
and composite materials due to its outstanding properties and
China
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c4ra01505c
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great versatility.26 Nonetheless, the water contact angle of the
common epoxy resin is less than 90ꢀ, which is said to be
hydrophilic.27 Admittedly, the epoxy resin serves as an adhesion
and stress relief layer, and the nanocomposite super-
hydrophobic surface showed improved mechanical robust-
2.3. Synthesis of bisphenol A diglycidyl ether monoacrylate
(AADGEBA)
The KOH (0.03 g) was dissolved in AA (0.75 g), and then the
solution was added to the mixture composed of DGEBA (3.92 g),
hydroquinone (0.37 g) and toluene (80 ml). The reaction was
carried out at 90–110 ꢀC for 4–7 h. Conrming the complete
conversion of the DGEBA by TLC, aerward similar treatments
were performed as those of DGEBA preparation, then AADGEBA
could be obtained as a slightly yellow, transparent liquid. The
synthesis process of AADGEBA is summarized in Scheme 2.
ness.28,29
Yang
and
co-workers
consequently
used
polydimethylsiloxane as a negative template to cure the epoxy
resin so as to obtain superhydrophobic surfaces with superior
mechanical properties.30
In order to take advantage of adhesive property of epoxy resin
and low surface energy of PS, we synthesized the copolymer of
styrene and bisphenol A diglycidyl ether monoacrylate (PS-co-
AADGEBA). Based on which, a transparent and robust poly-
meric superhydrophobic surface via phase separation method
was created. Furthermore, the PS-co-AADGEBA was also
successfully graed onto the surfaces of amino-functionalized
2.4. Synthesis of PS-co-AADGEBA
The synthesis of PS-co-AADGEBA is expressed in Scheme 3. Free-
radical copolymerization of St and AADGEBA was performed at
ꢀ
70 C in THF at nitrogen atmosphere using AIBN as the initi-
hollow silica nanospheres (HSNs-NH2), which was generated by
ator. Aer 48 h polymerization, copolymers of St and AADGEBA
were precipitated by ethanol and water (volume ratio of 2 : 8).
The precipitates were dissolved in acetone and reprecipitated by
ethanol and water for three times. ꢀSubsequently, the products
were dried in a vacuum oven at 30 C for 24 h.
31
¨
a modied Stober method.
2. Experimental section
2.1. Materials
St was puried through vacuum distillation before used. The
initiator azodiisobutyronitrile (AIBN) was puried by recrystal-
lization from absolute ethanol. Bisphenol A, epichlorohydrin
(EPI), sodium hydroxide (NaOH), acrylic acid (AA), potassium
hydroxide (KOH), hydroquinone, toluene, THF, tetraethyl
orthosilicate (TEOS), polyacrylic acid (PAA, molecular weight of
3000), ammonia hydroxide (28 wt%), 3-aminopropyl triethoxy-
silane (APTES), Na2SO4, ethyl acetate, petroleum ether,
dichloromethane, ethanol, acetone and distilled water were
used as received.
2.5. Fabrication of the PS-co-AADGEBA surface
The PS-co-AADGEBA (0.10 g) was dissolved in THF (4 ml) at the
reuxed temperature under stirring. Aerwards, the pure
ethanol was added into the solution. The glass substrates were
washed by using an ultrasonic generator for 30 min in ethanol
to remove the dust and dried in the air. A particulate lm was
thereupon developed by dispensing 0.5 ml of the dispersion
onto a cleaned glass substrate of 2 ꢁ 2 cm and evaporating
the solvent at room temperature. Meanwhile, the smooth
copolymer surface as a reference was prepared by directly
dropping the copolymer/THF solution onto the cleaned glass
substrate without adding any ethanol.
2.2. Synthesis of bisphenol A diglycidyl ether (DGEBA)
The synthesis of DGEBA is described in Scheme 1. A mixture of
Bisphenol A (5.7 g), EPI (9.25 g) and NaOH solution (10 M, 10
ml) was stirred in a ask at 70–80 ꢀC for 12 h. Aer conrming
the complete conversion of the Bisphenol A and the interme-
diate by TLC, distilled water (15 ml) and toluene (30 ml) were
added into the residue under vigorous stirring. The organic
layer was separated, and washed by water to neutral. Aerward,
it was dried over Na2SO4 and concentrated in vacuo to give the
crude product, which was puried by column chromatography
(ethyl acetate/petroleum ether ¼ 1/3) to provide DGEBA as a
viscous, transparent liquid.
2.6. Characterization
Bruker VERTEX-70 Fourier transform infrared (FTIR) spec-
trometer was used to investigate the DGEBA, AADGEBA and PS-
co-AADGEBA. H-nuclear magnetic resonance (1H NMR) spectra
of DGEBA, AADGEBA and PS-co-AADGEBA were obtained on a
Bruker AVANCE11400 spectrometer in CDCl3 at room temper-
ature. Molecular weights and molecular weight polydispersities
(Mw/Mn) of the copolymers were determined with a DAWN
HELEOS multiangle laser light scattering (MALLS) detector.
Thermogravimetric (TG) analyses were performed using a STA-
449C apparatus. The samples were heated from room temper-
ature to 800 ꢀC at a heating rate of 10 ꢀC minꢂ1 under nitrogen
purge. The glass transition temperatures (Tg) of polymers were
measured by a TAQ10 differential scanning calorimeter (DSC).
The measurements were performed from 60 to 140 ꢀC at a
heating rate of 10 ꢀC minꢂ1 under nitrogen purge. The
morphologies of the prepared surfaces were observed by scan-
ning electron microscopy (SEM, Hitachi S-4800, Japan) at an
accelerating voltage of 5 kV, and the WCA and SA were
measured on contact angle tester SL200B (Solon Technology
Scheme 1 Synthesis of DGEBA.
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Scheme 2 Synthesis of AADGEBA.
Scheme 3 Synthesis of PS-co-AADGEBA.
Science Co., Ltd) at ambient temperature with about 5 ml liquid stretching vibration of DGEBA is supported by the absorptions
droplets.
around 1251 and 1035 cmꢂ1. The peak at 1302 cmꢂ1, corre-
sponds to the stretch mode of C–C bond, and the one at 832
cmꢂ1 is C–H bending vibration of multi-substituted phenyl
ring.32 To sum up, the appearance of the above signals indicates
the formation of DGEBA.
3. Results and discussion
3.1. Characterization of DGEBA, AADGEBA and PS-co-
Fig. 1b shows characteristic absorptions of C]O, C]C
AADGEBA
appeared at 1728 and 1640 cmꢂ1 33 The absorption of fatty ether
.
bond (C–O) at 1035 cmꢂ1 is signicantly reduced, and the
amplitude at 3460 cmꢂ1 stretching vibration absorption of O–H
emerge clearly.
3.1.1. FTIR spectra of DGEBA, AADGEBA and PS-co-
AADGEBA. The structures of DGEBA, AADGEBA and PS-co-
AADGEBA were characterized by FTIR. As shown in Fig. 1a, the
characteristic absorptions of bisphenol A appear at 2964 cmꢂ1
(ys, CH3) and 2869 cmꢂ1 (ya, CH3) in the C–H stretching region,
respectively. The peaks at 1608, 1512 and 1455 cmꢂ1 are the
typical absorption of the C]C bond on the benzene ring, while
the presence of aromatic ether bond and fatty ether bond (C–O)
In Fig. 1c, the typical absorption of the monosubstituted
benzene ring is supported by the amplitudes around 755 and
697 cmꢂ1, and ve sharp peaks around 3000 cmꢂ1 are the
characteristic absorptions of polystyrene.34 At the same time,
the signal at 1640 cmꢂ1 disappears, demonstrating that the PS-
co-AADGEBA has been acquired.
3.1.2. 1H NMR spectra of DGEBA, AADGEBA and PS-co-
AADGEBA. 1H NMR spectra of DGEBA, AADGEBA and PS-co-
AADGEBA were obtained in CDCl3 at room temperature, as
1
shown in Fig. 2. The H NMR spectrum in Fig. 2a have char-
acteristic shi signals of DGEBA (d ¼ 7.14, 6.83, 4.26–2.70, 1.64
ppm). Assignments of these peaks are as follows: at 7.14 and
6.83 ppm to proton signals on the benzene ring (
at 4.26–2.70 ppm to the saturated proton signals (
and at 1.64 ppm to the saturated proton signals (
),
),
). The 1H
NMR spectrum of AADGEBA based on DGEBA is represented in
Fig. 2b. The 1H NMR spectra of DGEBA and AADGEBA are found
to be typical to each other except the presence of signals at 5.85–
6.55, and 2.06 ppm, corresponding to the protons of acrylate
(
) and hydroxyl groups (
), respectively. The
emergence of hydroxyl proton signals proves the occurrence of
1
ring-opening reaction of acrylic acid and DGEBA. The H NMR
Fig. 1 FTIR spectra of (a) DGEBA (b) AADGEBA (c) PS-co-AADGEBA.
spectrum in Fig. 2c has characteristic shi signals of PS
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Fig. 3 DSC curves of (a) PS-co-AADGEBA (b) PS.
Fig.
2
1H NMR spectra of (a) DGEBA (b) AADGEBA (c) PS-co-
AADGEBA.
(d ¼ 7.47–6.24, 2.33–0.79 ppm) and AADGEBA (d ¼ 4.23–2.70,
2.33–0.79 ppm), while proton signals at 5.85–6.55 ppm disap-
pear, which demonstrate the successful copolymerization of PS
and AADGEBA (see also the details on 1H NMR spectra of
DGEBA, AADGEBA and PS-co-AADGEBA in the ESI†).
Fig. 4 GPC curves of PS-co-AADGEBA.
3.2. Characterization of surface morphology
3.1.3. DSC curves of PS and PS-co-AADGEBA. The DSC
curves of PS and PS-co-AADGEBA are shown in Fig. 3. The glass
transition temperature (Tg) values of PS-co-AADGEBA (Fig. 3a) is
close to 80 ꢀC, lower than that of pure PS (Fig. 3b), which is
3.2.1. SEM images of the PS-co-AADGEBA surface. When
the solution of the copolymer/THF dried under ambient
temperature on the glass substrate by drop coating, the WCA of
the surface was measured to be 93.4ꢀ (Fig. 5a). With increasing
volume fraction of ethanol, the degree of copolymer phase
separation increased, resulting in the formation of rough
surfaces (Fig. 5b). The variation of contact angles of these
surfaces is shown in Fig. 6. It is evident that the maximum
contact angle is 155.2ꢀ and the best content of ethanol is about
50%. The surface prepared from the copolymer solution with
THF (50%) as solvent consists of numerous micron-sized
particles (Fig. 5c), and the large particles are about ten times the
size of the small particles. The investigations indubitably
revealed that the surface was superhydrophobic, possessing
water contact angles of ꢃ155.2ꢀ and water sliding angles of ꢃ4ꢀ.
3.2.2. Analysis of the surface morphology. The possible
formation mechanism of the PS-co-AADGEBA surface can be
described as follows (Fig. 7). Phase separation and self-assembly
ꢀ
approaching 98 C. Aer the polymerization of PS and AADG-
EBA, the number of benzene rings on the polymer chain
reduces, enriching the exibility of the polymer chain, so the Tg
values decreases correspondingly. In addition, DSC measure-
ments showed that both of them exhibit single glass transition
temperature, indicating that the products are the single
substance but blends.
3.1.4. GPC analysis of PS-co-AADGEBA. Fig. 4 shows the
GPC curves of PS-co-AADGEBA. The weighted-average molar
mass (Mw) and the number-average molecular weight (Mn) of PS-
co-AADGEBA, measured from MALLS, are about 1.421 ꢁ 104 and
1.195 ꢁ 104 g molꢂ1, respectively. So a fairly narrow molecular
weight distribution, Mw/Mn ¼ 1.189, were obtained.
In summary, all of the experimental results are coincident,
illustrating that the target copolymers has been obtained.
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Fig. 5 SEM images of the PS-co-AADGEBA surface with different ethanol contents in the copolymer/THF solution: (a) 0%; (b) 30%; (c) 50%; (d)
the (PS-co-AADGEBA)-g-(HSNs-NH2) surface.
Fig. 7 Schematic diagram for the formation of the PS-co-AADGEBA
surface.
Analysis of solvent parameters, rapid solvent evaporation
Fig. 6 The variation of water contact angles of the PS-co-AADGEBA
should produce a percolated polymer network, and slower
evaporation should be conducive to discrete particle formation.
The evaporation rate of ethanol (see Table 1) is lower than THF,
and the two solvents successively acted in forming micro-
particles. The differences in solubility parameters (9.5 and 11.3
MPa1/2) for the two solvents indicate that the mixture was more
polar and should be a better solvent for the AADGEBA. The polar
and hydrogen-bonding components of the solubility parameter
of ethanol are considerably larger than those from THF (see
Table 1), which suggests that the ethanol will preferentially
interact, or solvate, the polar segments, which will decrease the
dipolar interactions of the copolymer in solution and expand
the polymer chain.25
surface with different ethanol contents.
of amphiphilic PS-co-AADGEBA worked simultaneously, which
was a spontaneous process. In the beginning, the linear chains
of PS-co-AADGEBA stretched freely in copolymer solution, along
with the evaporation of solvent, the stretching PS-co-AADGEBA
chains in the solution self-assembled into spherical coils, then
aggregated to small particles with the groups of hydrophilic
inside and the ones of hydrophobic outside.35 In order to reduce
the surface energy further, some spherical particles will reunite
to form bigger particles and the small ones will attach them-
selves to the surfaces of the bigger ones.
To better understand the superhydrophobic property of the
prepared surface thoroughly, we veried the classical theory of
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Table 1 Solvent parameters
Hansen, solubility parameters (MPa1/2
)
Evaporation rate
Solvent
(N-BAC ¼ 1)
Total
Nonpolar
Polar
Hydrogen bonding
THF
Ethanol
THF/ethanol (v/v ¼ 1/1)
6.3
1.7–1.9
—
9.5
13
11.3
8.2
7.7
8
2.8
4.3
3.6
3.9
9.5
6.7
superhydrophobic surface on it. When a droplet placed on a
smooth surface, the intrinsic contact angle named Young's
contact angle (q) is given by the relative surface energies of the
solid–liquid (gSL), solid–air (gSA), and liquid–air (gLA) interfaces
as36
3.3.1. Corrosion and aging resistance evaluation. The
wettability of different liquids with pH values of 3 to 10 on the
PS-co-AADGEBA surface was studied. Strong acid and alkaline
liquid droplets contact angles are all above 150ꢀ as shown in
Fig. 8a, which illustrated that the surface we prepared possesses
superhydrophobic properties not only for pure water but also
for corrosive liquids. The result is very attractive for applications
in corrosive environments.
ꢀ
ꢁ
gSA ꢂ gSL
q ¼ cosꢂ1
(1)
gLA
As shown in Fig. 8c, the aging tests for the PS-co-AADGEBA
superhydrophobic surface were also conducted. The surface
was exposed indoor for 140 days at room temperature. The
water contact angles are still greater than 150ꢀ, notwithstanding
decrease a little, revealing excellent aging resistance for the PS-
co-AADGEBA superhydrophobic surface.
3.3.2. Transparency and mechanical robustness test.
Recently, more and more attention has been focused on
creating coatings with both superhydrophobic and transparent
properties.39 In this paper, a solution of the PS-co-AADGEBA
nanoparticles obtained via phase separation was dip-coated on
the surfaces of cleaned glass substrates. The transparency of the
surface was directly visible and the mechanical property of the
surface was observed by impact of water.
Wenzel proposed a model,37 shown in eqn (2) to describe the
wettability on a surface,
cos qr ¼ r cos q
(2)
Here, r is the roughness factor, and q and qr are the equilibrium
contact angles of a liquid on a smooth solid surface and a rough
solid surface, respectively. According to eqn (2), if the roughness
is increased, the contact angle of a hydrophobic solid surface
will increase also. The WCA of the surface of copolymer/THF
solution was measured 93.4ꢀ, which is an intrinsic hydrophobic
surface. Thus, according to the Wenzel model, we believe that
the rough surfaces observed in SEM by phase separation should
be more hydrophobic than the smooth one. The WCA of the
surface of copolymer/THF (50%) as solvent was measured
155.2ꢀ, which was consistent with the theory.
As a result, the PS-co-AADGEBA superhydrophobic surface
shows high light transmittance, which is visible in Fig. 9a and b.
Acid and alkali droplets indicate superhydrophobicity with
methyl orange and phenolphthalein indicator, respectively.
On the other hand, a droplet gently deposited on a rough
surface that favors the Cassie state energetically stays in the
Cassie state with a high contact angle as given by38
qr ¼ cosꢂ1(ꢂ1 + f(1 + cos q))
(3)
here qr is the WCA of the PS-co-AADGEBA superhydrophobic
surface, while q is the equilibrium WCA on the smooth PS-co-
AADGEBA surface and f is the solid area fraction dened as the
ratio of the projected area to the base area of the surface. Based
on the WCA data that were obtained (q ¼ 93.4ꢀ and qr ¼ 155.2ꢀ),
the value of f is calculated about 0.098 (<1). These results are
responsible for the superhydrophobic property.
3.3. Feature and characterization of surface property
With the epoxy group in side chain, the copolymer possesses
certainly adhesive properties, hence the mechanical robustness
of the superhydrophobic surface should be improved. In the
following paragraph, the corrosion and aging resistance, the
transparency and the mechanical robustness of the surface have
been examined to verify the speculation.
Fig. 8 CA as a function of pH value and exposure time for the PS-co-
AADGEBA surface (a and c) and the (PS-co-AADGEBA)-g-(HSNs-NH2)
surface (b and d), respectively.
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Fig. 9 Acid and alkali droplets on the PS-co-AADGEBA surface (a) acid droplets with methyl orange indicator (b) alkali droplets with phenol-
phthalein indicator (c) hot water of 50 ꢀC.
Moreover, it is also stable for hot water as hot as 50 ꢀC, as shown and condensation of –Si–(CH2)3–NH2 of APTES. The typical
in Fig. 9c. In order to investigate the stability of the super- absorption of the monosubstituted benzene ring is supported
hydrophobic surface against the impact of water, experiments by the peaks around 755 and 697 cmꢂ1, and peaks around 3000
were conducted by impinging the surface under running water. cmꢂ1 are the characteristic absorptions of polystyrene (Fig. 10c).
The surface, which can be seen via the video in the supporting
Fig. 11 shows TG curves of HSNs-NH2 and (PS-co-AADGEBA)-
materials, emerges good adhesion to the glass substrate and g-(HSNs-NH2). The silica remain stable up to about 800 ꢀC. The
remains integrated and superhydrophobic. It can be interpreted decomposition temperature at maximum rate (Tpeak) for (PS-co-
that a hydrogen bond generates when particles of PS-co-AADG- AADGEBA)-g-(HSNs-NH2) is approaching 350 ꢀC, which is
EBA land on the glass substrate, and the hydroxyls of epoxy accordant with the degradation of PS and DGEBA.41 Accord-
resin and the rich hydroxyls from the glass substrate tend to ingly, these results indicate that a 11.5% and a 26.5% loss were
combine together owing to the van der Waals interaction.40
observed for HSNs-NH2 and (PS-co-AADGEBA)-g-(HSNs-NH2),
respectively.
SEM images of the (PS-co-AADGEBA)-g-(HSNs-NH2) surface
are shown in Fig. 5d, rough structures of (PS-co-AADGEBA)-g-
(HSNs-NH2) and its aggregates guarantee a large amount of air
can be trapped at the surface, which is benecial for water
droplets roll on it. The investigations showed that the (PS-co-
AADGEBA)-g-(HSNs-NH2) surface was superhydrophobic, pos-
sessing water contact angles of ꢃ158.6ꢀ, and water sliding
angles of ꢃ3ꢀ.
3.4. Application of the copolymer
The PS-co-AADGEBA was also successfully graed onto the
surfaces of amino-functionalized hollow silica nanospheres
(HSNs-NH2), then
a (PS-co-AADGEBA)-g-(HSNs-NH2) nano-
composite superhydrophobic surface was prepared through
casting drops of (PS-co-AADGEBA)-g-(HSNs-NH2)/toluene on the
cleaned glass substrate (the details seen also in the ESI†).
To conrm the presence of amino groups on the surface of
HSNs, FTIR spectra of HSNs-NH2 were investigated by using the
pure HSNs as reference (Fig. 10a and b). The transmission
bands at 2920, 2850 cmꢂ1 assign to the asymmetric (yas)
stretching vibrations of methylene (CH2) from the hydrolysis
The superhydrophobic surface created with (PS-co-AADG-
EBA)-g-(HSNs-NH2) shows ideal corrosion and aging resistance,
as shown in Fig. 8b and d. But it has poor transparency and
weak resistance to the impact of water. Subsequent effort
should be focused on the transparency and mechanical
Fig. 10 FTIR spectra of (a) HSNs (b) HSNs-NH2 (c) (PS-co-AADGEBA)- Fig. 11 TG curves of (a) HSNs-NH2 (b) (PS-co-AADGEBA)-g-(HSNs-
g-(HSNs-NH2).
NH2).
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robustness of the nanocomposite superhydrophobic surface. 14 A. Yildirim, T. Khudiyev, B. Daglar, H. Budunoglu,
The transparency of HSNs superhydrophobic surface has been
reported by Ligang Xu.42 It is possible that the presence of epoxy
A. K. Okyay and M. Bayindir, ACS Appl. Mater. Interfaces,
2013, 5, 853.
groups in the (PS-co-AADGEBA)-g-(HSNs-NH2), and hence 15 E. Ueda and P. A. Levkin, Adv. Mater., 2013, 25, 1234.
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4. Conclusions
In summary, the copolymer of styrene and bisphenol A digly-
cidyl ether monoacrylate (PS-co-AADGEBA) was synthesized.
The novel polymeric superhydrophobic and a nanocomposite
superhydrophobic surface were fabricated based on the copol-
ymer. The polymeric surface was transparent and exhibited
improved mechanical robustness due to the presence of the
epoxy resin in the copolymer. Both the surfaces showed
attractive stability for corrosive liquids and excellent aging
resistance to withstand real world applications.
¨
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Acknowledgements
This work is supported by Shandong Province Natural Science
Foundation (ZR2012EMM009 and ZR2013EMQ005), the Scien-
tic Research Foundation for the Returned Overseas Scholars in
Jinan (20100406), National Natural Science Foundations of
China (51372140, 51303086 and 51172132), the Youth Scientist
Funds of Shandong Province (BS2011CL025).
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